Recognizing that outdoor exercise has the potential to improve physical and mental health as well as cognition, Park Prescriptions (ParkRx) was developed to promote both physical activity and exposure to nature among low-income populations. Children who grow up in poverty have lower levels of achievement, worse health, and experience higher stress. Both physical activity and exposure to nature have been associated with stress reduction and better cognitive functioning. That low-income populations spend less of their leisure time in physical activity and less of this physical activity time in outdoor settings than higher income populations, may, in part, explain health and achievement disparities. Park prescriptions are formal clinical encouragements for patients to engage in more physical activity outdoors. From the beginning, ParkRx has been perceived as a common-sense solution to physical inactivity and to increasing the time children might be spending outdoors in nature. In spite of a lack of rigorous evidence that it is effective, the ParkRx concept is currently being widely disseminated and has been embraced by multiple national organizations. Unity Health, a federally qualified community health center in Washington, DC, is currently implementing park prescriptions for its largely low-income and minority population, a group at high risk of chronic diseases, physical inactivity and obesity. In partnership with Unity Health, we propose to conduct a randomized controlled trial (RCT) to prospectively evaluate Park Rx?s impact on physical activity, as well as other secondary health outcomes in pediatric patients. Our specific aims are: 1) to test whether Park Rx will increase park visits and accelerometry-measured physical activity among children; 2) to identify any biological impacts of Park Rx on health, including impact on hypercholesterolemia, hypertriglyceridemia, HbA1C, overweight and obesity, for those patients with relevant diagnoses; 3) to explore impacts on mental health, including stress and measures of cognitive functioning; and 4) to determine whether there are age and gender differences in adherence to and impact of Park Rx. The results of this study will quantify the effectiveness of Park Rx and inform its future dissemination.